989
FXUS63 KMQT 012312
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
712 PM EDT Mon Jul 1 2024

.KEY MESSAGES...

-Our next round of rain showers, with some rumbles of thunder,
 moves in by early Tuesday morning.

-Two distinct rounds of precipitation for Tuesday: one in the
 morning and one late at night. Thunderstorm chances are around
 20%- 30% for each round.

-Low chance (~25%) of afternoon and low to medium chance
 (25-40%) of evening showers/storms across Upper Michigan on
 Independence Day. Rain spreads over the region Thursday night
 and Friday.

-Weather pattern remains active into the second week of July.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 306 PM EDT Mon Jul 1 2024

The upper ridge axis is sliding across the Great Lakes this
afternoon, with surface high pressure centered over the Lower
Peninsula. With increasing southerly winds over the UP and a warmer
airmass working in, temperatures have been able to climb into the
70s across the UP; some spots in the western half of the UP, where
southerly winds are downsloping, are even flirting with the 80
degree mark.

Clouds will gradually spread in through the first half of the night
ahead of a shortwave that is currently ejecting out of the Plains.
Not far behind will be the next round of rain showers by Tue 06Z. As
the showers track eastward across the UP tonight, also cannot rule
out a few rumbles of thunder...but will note that instability
remains quite limited with capped soundings. Meanwhile, much warmer
lows can be expected tonight unlike the last few nights as the
clouds/rain limit radiational cooling. Widespread 50s will prevail
Tuesday morning.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 411 PM EDT Mon Jul 1 2024

A pair of troughs traversing the central CONUS through this week
will be the driver of multiple rounds of precipitation which may
impact recreation around Independence Day. While uncertainty grows
significantly into the weekend, the general pattern indicates the
general active and wet pattern to continue, though with prevailing
northwesterly flow aloft, temperatures look to not be particularly
warmer than normal for July.

Tuesday morning, showers will be ongoing in the western UP and will
be passing into the central and eastern UP throughout the day.
Models continue to trend downwards regarding available instability,
so chances of thunderstorms are limited to around 20% early in the
west and any thunderstorms should be weak. Rainfall totals are also
expected to be fairly low with the 12Z HREF showing 24-hourly
precipitation chances greater than an inch of 10% or less. A lull is
expected by afternoon in the west, which will shift east through the
evening as the initial swath of precip exits into Ontario. As this
initial wave moves through, a strengthening pressure gradient over
the region will ensue as a strong 925-850mb 40-50kt low level jet
presses overhead. Even with modest diurnal mixing, gusty southerly
winds will develop, particularly near the Bay of Green Bay, Lake
Michigan, and the downslope and higher terrain locations in the
Gogebic Range, Michigamme Highlands, and lakeshore areas of
Marquette and Alger counties. The HREF highlights wide swaths of
area over the UP that could see 40-60% chance of 40+mph gusts,
though the 12Z Euro mostly limits this to the higher terrain along
Lake Superior. Model soundings that suggest effective mixing suggest
potential upwards of 40 mph. The second wave will lift northeast
into the UP Tuesday night ahead of the eastward migrating cold front
draped from the GEFS-mean 992mb low over far northern Ontario.
MUCAPE looks a little better with this round of precipitation, but
thunder chances still remain 30% or below.

A surface ridge extending northwest should help support a mostly dry
day on Wednesday, although there is a brief period in the east that
could destabilize enough for afternoon showers/storms to develop
before the cold front clears. The 4th of July should start off dry
thanks to the lingering effects of the surface ridge and a meso high
developing over Lake Superior at around 1015mb. Upstream though,
another trough exits the northern Rockies and presses through the
Plains. Guidance amplifies the shortwave and lifts a surface low
through the eastern Dakotas and into Minnesota in the
afternoon/evening. There`s good agreement among the guidance
packages that this wave will shift east through Minnesota and
Wisconsin through the day Friday, then lift northeast through Upper
Michigan Friday night into early Saturday. Best chances for precip
with this wave will be Thursday night and Friday. Its unclear if it
will remain dry Thursday afternoon and evening in the western half
of Upper Michigan. While probability is currently low (~25%),
Thursday afternoon destabilization could result in convection
developing. Additionally, increasing isentropic ascent may support
showers lifting into the region during the evening hours (25-40%).
Anyone with evening firework plans across the western half of Upper
Michigan should continue monitoring the forecasts.

Ensembles then diverge significantly beyond the departure of showers
on Saturday, but the general overall pattern remains amplified
with plenty of distinct chances for precipitation under passing
low pressure systems. Ensemble mean 500mb charts show the
preference for ridging over the western Atlantic and western
CONUS, putting the UP under a preferred northwesterly flow,
which helps keep temperatures from getting too hot, but is still
active enough to keep wetter than normal precipitation into the
second week of July.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 711 PM EDT Mon Jul 1 2024

VFR conditions prevail at the start of the TAF period under mainly
clear skies. A strengthening pressure gradient will keep southerly
winds gusting to 20-25 kt overnight at IWD/SAW. The southerly winds
will eventually usher in more moisture, allowing showers to spread
across the terminals from west to east late tonight into Tuesday
morning. A 40-50 kt low level jet will result in low level wind
shear conditions late tonight at IWD, then developing Tuesday
morning at CMX/SAW. Some of the stronger winds will mix to the
surface, with southerly wind gusts of 30 kt possible for much of the
day. MVFR cigs are expected to gradually develop Tuesday morning,
persisting much of the day. There is around a 30% chance of IFR cigs
developing at IWD/SAW during the day Tuesday, but probs not high
enough to keep prevailing in the TAFs at this time.

&&

.MARINE...
Issued at 411 PM EDT Mon Jul 1 2024

High pressure continues to create light wind conditions over Lake
Superior, but this high is weakening and shifting east this
evening, so tranquil conditions will be short-lived.

A system will begin lifting from the Plains into Canada tonight,
then continue lifting northward Tuesday into Wednesday. The passage
of this system will result in at least two rounds of rain and storms
and two periods of stronger winds. Expecting the first round of
showers, with a 20% chance of thunderstorms embedded within, to
shift through Lake Superior late tonight and Tuesday. These showers
may (20-40% chance) support fog developing and periods of low
visibility on the lake. As the system approaches tonight, tightening
pressure gradient will develop while a strong 40-50kt 925-850mb low
level jet moves over eastern Lake Superior. Model guidance remains
uncertain in how much of these stronger winds will mix to down to
the surface given the increasing stability of the over lake
environment. However, recent internal probabilistic tools are
beginning to highlight nearshore areas downwind of the Michigan
lakeshores and the stretch from Marquette northward into Canadian
waters as those most likely to experience low end gales. Between
internal guidance, the HREF, and Euro guidance, probabilities of
gales remain around 20-40%. These ~40% values may also be somewhat
representative downwind of the lakeshores east of Marquette and
along the northern shores of the Keweenaw, where models struggle
with the land/lake interface and localized terrain driven influences
have been known to mix down stronger winds to the surface. At this
point, given the uncertainty and the isolated nature of the stronger
mixing downwind of the lakeshores, will continue to hold off on
gale headlines.

Another round of moisture will lift through Tuesday night into
Wednesday while the effects of the low level jet wane. The cold
front presses through west to east Tuesday night into Wednesday
morning, allowing winds to become westerly/southwesterly for
Wednesday. Another period of stronger winds up to 20-30kts, looks
possible between the Keweenaw and Isle Royale Wednesday in this
southwesterly flow. High pressure returns briefly for Thursday with
a weaker low pressure system expected to pass over the Upper Great
Lakes late Friday and Saturday. Light winds below 20 kts returns
Wednesday night, continuing likely into the weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...LC
LONG TERM...GS/JTP
AVIATION...Thompson
MARINE...GS/JTP